Made some time to continue the experiments with the D3a today. Having got triode and pentode mode working I wanted to try ultralinear, suggested by Jac of JacMusic.
Choke load, LL1667-20mA (200H). The two coils of the LL1667 are connected in series (correct polarity observed), anode connected to output from the choke, g2 connected to the mid-point. 47K grid load, 100K output load.
g2 measures at 5mA, Ia = 17mA, Ik = 22mA, Vak = 157V.
Interestingly though, the square wave input at the grid becomes horribly distorted at the output. Looks like overshoot and ringing ?
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